1. Field of the Invention
This invention relates in general to compensating for errors in the trajectory of ballistic reentry bodies and, in particular, to a method of compensating for such errors by adjusting the fuzing location.
2. Description of Prior Art
It is well known that the theoretical trajectory of ballistic missiles can be predetermined with great accuracy. Consequently, the so-called "nominal" position of the missile at any time in flight can be predicted. However, because of errors generated by the weapon delivery system, the standard deviation of the weapon system delivery dispersion at nominal reentry time is described by an inclined ellipsoid in the trajectory plane. Conventional fuzing subsystems utilize combinations of impact fuzing, fuzing at a radar measured altitude, and fuzing at a predetermined time after encountering a given longitudinal deceleration level. With these fuzing techniques, the dispersion ellipsoid is propogated along the trajectory to yield an elongated downrange-crossrange ellipse at the fuzing location. The downrange dispersion caused by errors generated in the weapon delivery system limits the predictable effectiveness of the ballistic reentry body upon the target.
One approach for reducing the downrange errors generated in the delivery system is described in the U.S. Pat. No. 3,990,657. In this approach, the downrange error is reduced by determining the altitude error from the nominal at a particular time during flight, computing a position error from this altitude error, and then maneuvering the reentry body in flight to return the reentry body to its nominal trajectory. A major disadvantage of this method is, of course, that means must be provided for manuevering the reentry body to change the ballistic trajectory.